Typically couplings according to the invention are used in pressure systems where the pressure hose is carrying pneumatic fluidic or hydraulic pressure for controlling various devices. In such systems a large number of different pressure hoses are provided, connecting different process or equipment controllers, valves, relays and the like, with a source of pressure. Usually such systems are assembled by hand, and the hose is cut to length as desired. The valves, controllers and the like are formed with one or more female threaded bores, and male threaded screw-in couplings are fastened therein. The lengths of hose are then secured to the screw-in couplings by means of which they are thus connected to the valves, controllers and other members. In the past, there have been numerous designs of such couplings. Generally speaking, they must meet three general requirements. They must be simple and easy to assemble by hand. They must provide a good pneumatic or hydraulic seal, within the ranges of pressure for which the system is intended. They must be cheap to manufacture and sell, since they will be used in large numbers.
Generally speaking, however, the prior art couplings have been of relatively complex multi-part construction, inevitably leading to a relatively costly assembly. In addition, the multi-part construction of such earlier couplings has introduced problems in providing a good seal.
In such couplings, it is particularly desireable to provide a screw threaded body portion, which may for instance be screw threaded into the particular recess to which the hose is to be connected, and the hose itself being then introduced into the body portion, and fastened and sealed without the use of further threaded fasteners. It is somewhat disadvantageous if a second threaded fastener is used, since the tightening down of such a further threaded fastener may cause the hose to twist, or may in some cases damage the hose or coupling as a result of over tightening and is for these reasons undesirable.
In order to overcome this problem, it has been proposed to provide a hose coupling of this type, having a linear hose clamping or fastening action. Such a coupling consisted of a threaded metallic body, and a plastic sleeve having a plurality of fingers extending around the hose. A sliding collar was provided around the exterior of such fingers with a wedging action so that when the collar was drawn along the sleeve away from the threaded body, it squeezed the fingers tightly together against the hose. When it is pushed in the opposite direction towards the threaded body, it released the fingers allowing the hose to be removed. In this system, the arrangement of the sleeve and fingers was manufactured separately from the threaded body, and was held in position in the threaded body in a relatively flimsy unsatisfactory manner, and required the use of a separate O-ring to provide a pneumatic seal.
The fingers were held in place in a recess in the metal body by a simple friction or push fit. Often the parts became disassembled in shipping or storage. Once assembled with the hoses, however, any movement of the hose, particularly a bending movement close to the coupling, was likely to separate the fingers from the metal body. In addition, since this unit was a multi-part construction, the manufacturing cost was relatively high.